Laser-induced thermal transfer processes are well-known in applications such as color proofing and lithography. Such laser-induced processes include, for example, dye sublimation, dye transfer, melt transfer, and ablative material transfer. These processes have been described in, for example, Baldock, U.K. Patent 2,083,726; DeBoer, U.S. Pat. No. 4,942,141; Kellogg, U.S. Pat. No. 5,019,549; Evans, U.S. Pat. No. 4,948,776; Foley et al., U.S. Pat. No. 5,156,938; Ellis et al., U.S. Pat. No. 5,171,650; and Koshizuka et al., U.S. Pat. No. 4,643,917.
Laser-induced processes use a laserable assemblage comprising (a) a donor element that contains the imageable component, i.e., the material to be transferred, and (b) a receiver element that are in contact. The laserable assemblage is imagewise exposed by a laser, usually an infrared laser, resulting in transfer of material from the donor element to the receiver element. The (imagewise) exposure takes place only in a small, selected region of the laserable assemblage at one time, so that transfer of material from the donor element to the receiver element can be built up one pixel at a time. Computer control produces transfer with high resolution and at high speed. The laserable assemblage, upon imagewise exposure to a laser as described supra, is henceforth termed an imaged laserable assemblage.
For the preparation of images for proofing applications and in photomask fabrication, the imageable component is a colorant. For the preparation of lithographic printing plates, the imageable component is an olephilic material which will receive and transfer ink in printing.
Laser-induced processes are fast and result in transfer of material with high resolution. However, in many cases, the resulting transferred material does not have the required durability of the transferred image. In dye sublimation processes, light-fastness is frequently lacking. In ablative and melt transfer processes, poor adhesion and/or durability can be a problem. In U.S. Pat. No. 5,563,019 and U.S. Pat. No. 5,523,192, improved multilayer thermal imaging elements and associated processes are disclosed that do afford improved adhesion and/or durability of the transferred images. However, there is a continuing need for still further improved thermal imaging assemblages and associated processes having improved image transfer efficiency and higher sensitivity of the assemblages.
Photosensitive elements which can be used to make relief images are well known. The photosensitive compositions generally comprise a photoinitiator and a component which is capable of reacting with the initiator, after it has been activated by exposure to actinic radiation. The reaction of the initiator and the second component produces a change in the physical properties of the layer such that the exposed areas can be differentiated from the nonexposed areas.
Imagewise exposure of a photosensitive element as currently known to the art generally requires the use of a phototool which is a mask (photomask) having clear and opaque areas covering the photosensitive layer (e.g., photoimageable and/or photopolymerizable layer). The phototool prevents exposure and photoreaction in the non-image areas, so that the image can be later developed. The phototool is clear, i.e., transparent to actinic radiation, in the image areas so that those areas are exposed to radiation. The phototool is usually a photographic negative (or positive) of the desired printing image. If corrections are needed in the final image a new negative (or positive) should be made. This is a time-consuming process. In addition, the phototool may change slightly in dimension due to changes in temperature and humidity. Thus, the same phototool, when used at different times or in different environments, may give different results and could cause registration problems.
Thus, it would be desirable to eliminate the practice of multiple use of a phototool and having to accurately align a phototool prior to imagewise exposure to avoid registration problems by digitally recording a phototool on a photo-sensitive element.
Additionally, liquid crystal display (LCD) devices have become increasingly important in displays which require very low consumption of electrical power or where the environment dictates a lightweight, planar, flat surface. For example, LCDs are used in display devices such as wristwatches, pocket and personal computers, aircraft cockpit displays, etc. However, there is a need to incorporate a color display capability into such monochrome display devices. A color filter array element typically includes the additive primary colors red, green, and blue in a black mosaic pattern. For the device to have color capability, each pixel should be aligned with a color area, e.g., red, green, or blue, of a color filter array. Depending upon the image to be displayed, one or more of the pixel electrodes is energized during display operation to allow full light, no light, or partial light to be transmitted through the color filter area associated with that pixel. The image perceived by a user is a blending of colors formed by the transmission of light through adjacent color filter areas.
A major contributor of the cost of LCDs is the color filter. The cost of producing color filters for LCDs has been very difficult to reduce because of a muliplicity of factors such as process complexity, color purity, temperature stability, and pattern fidelity. Four alternative manufacturing methods are considered to be useful for color filter production, dye gelatin, pigmented photoresist, electrodeposition and printing. Although dyes offer high transmittance and color purity they suffer from light and heat stability problems. In electrodeposition, the shape of the electrodes used for electrodeposition restricts arrangement of pixels. The printing method has also significant alignment and shape problems. The latter two methods do not allow forming fine dot patterns and, therefore, are not used in high information displays. The use of pigmented photoresist is generally the preferred method for producing color filters since both technically and economically it is the most feasible method for high quality and performance color filters. The overall size and resolution allows for the use of conventional photolithographic materials for the photoresist application. However, the problem associated with the preferred pigmented photoresist method is that the materials require numerous (.about.20 to 30 sequential) steps and wet chemistry to produce the color filter.
Thus, there is a need to greatly simplify the production of color filter arrays to reduce cost in order to meet the growing demand for color filter capability in LCDs.